To select a route in a network, there has been a method, performed by one node in the network, for calculating a preferable route among nodes, storing results from the route calculation in a tree-shaped form, and supporting the calculation of the preferable route. According to the above-described method, the number of calculation desired for formation of a tree coupling arbitrary two nodes may be reduced.
There is a packet transfer device that includes a routing table with two different functions in line cards of the packet transfer device. A first routing table is a local routing table that records transfer information that is frequently used as a sequential group. A second routing table is a distribution shared routing table that records the transfer information in such a way that the transfer information is distributed and does not match the other line card in the packet transfer device and that all the distributed information matches all the transfer information held in the packet transfer device.
There is a route information management device that includes a database, in which an Internet protocol (IP) address of a communication device and communication data to be transmitted to the communication device are stored in association with each other, and a calculating unit, which obtains the route information transmitted from another decide and calculates a route chart based on the route information, and a database updating unit, which reflects the route chart calculated by the calculating unit on the database. For example, Japanese Laid-open Patent Publication No. 3-139936, Japanese Laid-open Patent Publication No. 2006-313949, and Japanese Laid-open Patent Publication No. 2009-188573 are disclosed as the related art.